Heart block occurred in 214 patients (12%); 113 (6.3%) had
heart block on presentation and 101 (5.7%) developed
heart block in the 24 h
after treatment with rt-PA. Patients with
heart block at entry were slightly older and a greater proportion had
cardiogenic shock. The 21-day mortality rate among patients with
heart block at entry was 7.1% (8 of 113), compared with 2.7% (45 of 1,673) among patients without
heart block at study entry (relative risk 2.6, p = 0.007). However,
heart block was not independently associated with 21-day mortality after adjustment for other variables, including
shock. Mortality and other
adverse cardiac events in the following year were similar among patients with and without
heart block. Among patients without
heart block at study entry, coronary angiography among patients randomly assigned to coronary catheterization 18 to 48 h after admission revealed that the
infarct-related artery was occluded in 28.2% (11 of 39) of patients who developed
heart block versus 15.5% (112 of 723) of patients without
heart block (p = 0.04). The 21-day mortality rate was increased among patients in whom
heart block developed after
thrombolytic therapy (9.9% [10 of 101] versus 2.2% [35 of 1,572] of patients without
heart block, relative risk 4.5, p less than 0.001). Analysis of the increased mortality among patients who developed
heart block suggests that mortality was due to severe cardiac dysfunction; no patient was considered to have died as a result of the
heart block or its treatment.
CONCLUSIONS:
Heart block is common among patients with inferior
infarction given
thrombolytic therapy and is associated with increased mortality. These clinical and anatomic data provide insight into the mechanism of
heart block and increased mortality among such patients.